Room-Temperature Synthesis of Widely Tunable Formamidinium Lead Halide. Duong Nguyen Minh, Juwon Kim, Jinho Hyon, Jae Hyun Sim, Haneen H.

Transcription

1 Supporting Information Room-Temperature Synthesis of Widely Tunable Formamidinium Lead Halide Perovskite Nanocrystals Duong Nguyen Minh, Juwon Kim, Jinho Hyon, Jae Hyun Sim, Haneen H. Sowlih, Chunhee Seo, Jihye Nam, Sangwon Eom, Soyeon Suk, Sangheon Lee, Eunjoo Kim and Youngjong Kang* 1

2 Experimental Details A. Materials PbCl 2 (98%, Sigma-Aldrich), PbBr 2 (98%, Sigma-Aldrich), PbI 2 (99%, Sigma-Aldrich), formamidine acetate ( 98%, TCI), hydrobromic acid (HBr, 48%, Sigma-Aldrich), hydriodic acid (HI, 57%, Alfa Aesar), hydrochloric acid (HCl, 35-37%, Daejung), dimethylsulfoxide (DMSO, 99.5%, Daejung), anhydrous N-dimethylformamide (DMF, 99.8%, Sigma-Aldrich), anhydrous toluene (99.8%, Sigma-Aldrich), oleylamine technical grade (OLA, 70%, Sigma-Aldrich), oleic acid (OLAc, 99%, Sigma-Aldrich), methylamine (33 wt% in absolute ethanol, Sigma-Aldrich), octylamine (99%, Sigma- Aldrich). All products were used as-received without further purification. B. Preparation of PbX 2 -DMSO complexes PbI 2 -DMSO: PbI 2 -DMSO was synthesized following the procedures reported somewhere else. 1 PbI 2 (1 g) was dissolved in 3 ml of DMSO at 60 o C, the solution was stirred for 12 hr, and then 7 ml of toluene was slowly added with vigorous stirring. The resulting white precipitate was filtered and dried for 3 hr at room temperature. The final PbI 2 -DMSO powder was obtained by annealing at 60 o C for 24 hr under vacuum. PbBr 2 -DMSO: PbBr 2 -DMSO was synthesized following the same procedures above, but with slightly different chemical amount and heating temperature. 1 g of PbBr 2 was dissolved in 7 ml of DMSO at 70 o C, and precipitated by adding 20 ml of toluene. PbCl 2 -DMSO: PbCl 2 has a poor solubility in DMSO. PbCl 2 (1 g) was dissolved in a large amount of DMSO (15 ml) with vigorous stirring at 90 o C for 12 hr. Some of 2

3 undissolved solid was removed by filtration. 35 ml of toluene was poured into the filtrate to get the white precipitate. The isolated powder was dried at 60 o C for 24 hr. C. Preparation of formamidinium halide Formamidinium halide (FAX) (X=Br, Cl, I) was prepared following the previous report. 2 For the synthesis of FAI, formamidinium acetate powder (10.41 g) was added to an aqueous HI solution (57%, 20 ml), and stirred at 50 o C for 10 min. The solution was, then, transferred to a glass petri dish and heated at 100 o C for 2 hr. The resulting yellowish white powder was washed with diethyl ether and recrystallized in ethanol. Finally, the powder was dried overnight at 60 o C in vacuum oven, before use. FABr and FACl were also synthesized by the same procedures. D. Preparation of FAPbX 3 nanocrystals. FAPbBr 3 nanocrystals: For the synthesis of FAPbBr 3 nanocrystals, the precursor solution was first prepared by mixing 0.5 ml of PbBr 2 -DMSO (0.1 M in DMF), 0.5 ml of FABr (0.1 M in DMF), 5-25 μl of OLA, and 3.5 ml of anhydrous DMF. The precursor solution was then transferred in dropwise into copious amount of toluene (175 ml)/olac (787 μl) mixture with vigorous stirring.. Upon mixing with toluene, the solution immediately became pale green. Finally, some large particles were removed from the FAPbBr 3 nanocrystal solution by centrifugation at 5300 RCF (at 7000 rpm). FAPb(Cl 1-α /Br α ) 3 nanocrystals: Firstly, suitable amount of PbCl 2 -DMSO (0.1 M in DMF) or PbBr 2 -DMSO (0.1 M in DMF) was mixed with a certain amount of FACl (0.1 M in DMF) and FABr (0.1 M in DMF). For an example, 0.5 ml of PbCl 2 -DMSO was mixed with 0.3 ml of FACl and 0.2 FABr for the synthesis of FAPb(Cl 0.8 /Br 0.2 ) 3.The 3

4 mixture was then mixed with 10 μl of OLA, and 3.5 ml of anhydrous DMF to make the precursor solution. The rest other procedures were same as above. FAPb(Br 1-β /I β ) 3 nanocrystals: PbBr 2 -DMSO (0.1 M in DMF) or PbI 2 -DMSO (0.1 M in DMF) was reacted with a suitable amount of FABr (0.1 M in DMF) and FAI (0.1 M in DMF), and the procedures were same as above. E. Thermal stability tests 50 ml of FAPbBr 3 and MAPbBr 3 nanocrystal solutions in toluene were immersed in an oil bath pre-heated at 100 o C. Small aliquot (3 ml) of each solution was taken every 5 min for PL measurement. F. Instruments FTIR spectra were taken on Bruker LUMOS FTIR Microscope using transmission mode. UV-Vis absorption spectra were recorded on an Agilent Technologies 8453 UV-Vis spectrophotometer. PL emission spectra of colloidal solutions were measured on Fluoromate FS-2 fluorescent spectrometer (Scinco, Korea). PLQY of FAPbBr 3 nanocrystals was calculated followed the standard procedure using fluorescein standard. 3-5 Perkin Elmer LS 55 fluorescence spectrometers was used to investigate the thermal stability of FAPbBr 3 and MAPbBr 3 nanocrystals. Transmission electron microscope (TEM) images were taken on JEOL JEM-2100F. XRD samples were prepared by drop casting of FAPbX 3 solutions onto Si wafers. XRD patterns were recorded on a high resolution Rigaku Smartlab X-ray diffractometer or on Rigaku Ultima IV powder X-ray diffractometer, using the θ-2θ mode. The scanning speed was 1.33 /min. Lifetime of FAPbBr 3 and MAPbBr 3 nanocrystals were recorded with Edinburgh Instruments FL920 fluorescent spectrometer. 4

5 Figure S1. PbCl 2 -DMSO, PbBr 2 -DMSO and PbI 2 -DMSO from left to right, respectively. 5

6 Figure S2. a) Perovskite nanocrystals synthesized by using PbB 2 -DMSO precursors [FAPbBr 3 (DMSO) & MAPbBr 3 (DMSO)] and by using the conventional PbBr 2 [MAPbBr 3 ]. b) The corresponding PL emission spectra. 6

7 Figure S3. The solid state reaction of PbBr 2 -DMSO and FABr. Upon mixing PbBr 2 - DMSO powder with FABr powder, the mixture powder turned to pale green (left), and show fluorescence under the UV light (right). 7

8 ` Figure S4. PLQY of FAPbBr 3 was obtained from the relative method xx = ssss FF xx ff ssss nn xx 2 FF ssss ff xx nn ssss 2 using a fluorescein standard (PLQY fluorescein = 89%), where F x, F st, f x, f st, n x and n st are the integral photon flux, the absorption factor and the refractive index of sample and standard, respectively. In this case, the ratios, F x /f x and F st /f st can be directly obtained from the slopes of the graph (F x /f x = and F st /f st = ). 3-5 The refractive indices of sample and standard were n x =1.5 (toluene) and n st =1.33 (water). 8

9 Figure S5. PL emission spectra (solid lines) and UV-Vis absorbance spectra (dashed lines) of MAPbBr 3 nanocrystals, FAPbBr 3 nanocrystals and FAPbBr 3 precipitates collected by centrifugation at 5300 RCF. 9

10 Figure S6. PL emission (solid lines) and absorbance spectra (dashed lines) of FAPbBr 3 nanocrystals after purification by centrifugation at RCF. 10

11 Figure S7. PL emission spectra (solid lines) and corresponding UV-Vis absorbance spectra (dashed lines) of a) FAPb(Cl 1-α /Br α ) 3 at γ = 1.0, b) FAPb(Br 1-β /I β ) 3 at γ = 1.0, and c) FAPb(Br 1-β /I β ) 3 at γ =

12 Figure S8. Comparison of PL emission spectra of FAPb(Br 1-β /I β ) 3 synthesized at the condition of γ = 1.0 and γ =

13 Figure S9. Photograph image of FAPb(Br 1-β /I β ) 3 synthesized at the condition of γ = 0.8 under UV irradiation (λ peak = 365 nm). 13

14 Figure S10. Stability test of MAPbBr 3 and FAPbBr 3 nanocrystals under high humidity condition (RH = 85%). 14

15 Table S1. Time-resolved PL data and fitting information a MAPbBr 3 NCs FAPbBr 3 NCs FAPbBr 3 Precipitate Lifetime (ns) Relative (%) Lifetime (ns) Relative (%) Lifetime (ns) Relative (%) τ τ τ τ avg a Fitting equation: A + B 1 exp(-t/ τ 1 ) + B 2 exp(-t/ τ 2 ) + B 3 exp(-t/ τ 3 ) 15

16 Table S2. Lifetime of FAPbBr 3 nanocrystals purified by centrifugation at different g- force Purified at 5300 RCF Purified at 5700 RCF Purified at 6000 RCF Lifetime (ns) Relative (%) Lifetime (ns) Relative (%) Lifetime (ns) Relative (%) τ τ τ τ avg

17 Table S3. Lifetime change of FAPbBr 3 nanocrystals isolated by sequential centrifugations at 6000 & RCF 1 st FAPbBr 3 a 2 nd FAPbBr 3 precipitate b 2 nd FAPbBr 3 supernatant c Lifetime (ns) Relative (%) Lifetime (ns) Relative (%) Lifetime (ns) Relative (%) τ τ τ τ avg a 1 st FAPbBr 3 represents the nanocrystal solution obtained by centrifugation at 6000 RCF. b 2 nd FAPbBr 3 precipitate represents the precipitate of 1 st FAPbBr 3 solution collected by centrifugation at RCF. c 2 nd FAPbBr 3 supernatant represents the supernatant of 1 st FAPbBr 3 solution collected by centrifugation at RCF. 17

18 Table S4. Analysis of XRD patterns FAPbBr 3 precipitate at 5300 RCF FAPbBr 3 nanocrystals FAPbBr 3 purified at RCF FAPbBr 3 supernatant at RCF a (hkl) 2θθ d(a ) 2θθ d(a ) 2θθ d(a ) 2θθ d(a ) (100) (110) (200) (210) (220) (221) (300) a The peaks at 2θ = 11.27º, 13.14º, 17.01º and 19.30º are originated from 2D nanoplatelets of L 2 [FAPbX 3 ]n-1pbx 4 with n=1 or 2. 18

19 Table S5. Analysis of PL emission spectra of FAPb(Cl 1-α /Br α ) 3 and FAPb(Br 1-β /I β ) 3 Sample FAPbX 3 Emission Peak (nm) FWHM (nm) 1 FAPbCl FAPb(Cl 0.8 Br 0.2 ) FAPb(Cl 0.6 Br 0.4 ) FAPb(Cl 0.4 Br 0.6 ) FAPb(Cl 0.2 Br 0.8 ) FAPbBr FAPb(Br 0.6 I 0.4 ) FAPb(Br 0.4 I 0.6 ) FAPb(Br 0.3 I 0.7 ) FAPb(Br 0.2 I 0.8 ) FAPb(Br 0.05 I 0.95 ) FAPbI

20 Reference 1. Yang, W. S.; Noh, J. H.; Jeon, N. J.; Kim, Y. C.; Ryu, S.; Seo, J.; Seok, S. I., SOLAR CELLS. High-Performance Photovoltaic Perovskite Layers Fabricated Through Intramolecular Exchange. Science 2015, 348, Eperon, G. E.; Stranks, S. D.; Menelaou, C.; Johnston, M. B.; Herz, L. M.; Snaith, H. J., Formamidinium Lead Trihalide: A Broadly Tunable Perovskite for Efficient Planar Heterojunction Solar Cells. Energy Environ. Sci. 2014, 7, Würth, C.; Grabolle, M.; Pauli, J.; Spieles, M.; Resch-Genger, U., Relative And Absolute Determination of Fluorescence Quantum Yields of Transparent Samples. Nat. Protoc. 2013, 8, Grabolle, M.; Spieles, M.; Lesnyak, V.; Gaponik, N.; Eychmüller, A.; Resch- Genger, U., Determination of The Fluorescence Quantum Yield of Quantum Dots: Suitable Procedures and Achievable Uncertainties. Anal. Chem. 2009, 81, Brouwer, A. M., Standards For Photoluminescence Quantum Yield Measurements in Solution. Pure Appl. Chem. 2011, 83,